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Seems like they are going to exploit the elliptical orbit to collect & store the science data during the perihelion and download during the aphelion:
"From an operational perspective, Solar Probe1 orbits are divided into aphelion and perihelion segments. While some science data will be taken at a low rate throughout an orbit, most of the science data will be acquired during the solar encounters around perihelion. Encounter data will be stored on the redundant SSRs and played back, along with any cruise data acquired since the last ground contact, when the spacecraft is outside 0.59 AU, in the aphelion segment of the orbit."
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"the Earth–Probe distance varies from 0.3 AU to 1.9 AU"
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Attitude control:
"Solar Probe1 will be subjected to several environmental effects that must be taken into account in developing the design of the Guidance & Control subsystem. First, as the spacecraft approaches perihelion, sunlight reflected off of dust particles will be seen by a star tracker that is viewing the sky through the corona. Coronal lighting reduces the signal-to-noise ratio for a tracker using a CCD, thereby reducing the number of detectable stars and degrading the performance of the star tracker. As noted above, this effect will be mitigated by using multiple trackers and carefully selecting those that will perform well in the elevated background noise of the near-Sun environment."
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Solar radiation pressure will be very high and change rapidly during solar encounters. Because the center of photon pressure is ahead of the center of mass, the solar pressure torque is destabilizing and is an important factor in the dynamics of the spacecraft near perihelion.
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Dust problems:
"Dust impacts can also affect spacecraft attitude, especially near perihelion. Dust particles hitting the spacecraft will impart an instantaneous momentum impulse that the reaction wheels must remove. If the momentum impulse is too large for the wheels to handle, the thrusters will have be fired to keep the spacecraft oriented so that the sensitive spacecraft systems remain safely within the protective shadow of the TPS."
This list goes on. This is just a small sample of the 'challenges'.
Bottom line is that this thing will have to be be an engineering masterpiece!!
Cheers
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